The present invention relates to a method of increasing the stability of aqueous pyrethroid insecticidal formulations when stored in polyvinyl chloride (PVC) containers. Additionally, the present invention relates to improved pyrethroid insecticidal formulations that are stable in PVC containers.
Synthetic pyrethroid insecticides and naturally occurring pyrethrins, hereinafter collectively referred to as "pyrethroids", are a valuable class of insecticides available for controlling insects. The pyrethroids have very low solubility in water and are generally considered to be water insoluble. Because of their water insolubility, pyrethroids are usually formulated as an oil-in-water emulsion or microemulsion. However, aqueous pyrethroid formulations are unstable in polyvinyl chloride (PVC) containers. PVC containers are generally considered the container of choice because of their cost and ready availability. Due to the instability of aqueous pyrethroid emulsions in PVC containers, aqueous pyrethroid formulations are limited to packaging in glass or other plastic containers.
It is, therefore, desirable to provide a method for increasing the stability of aqueous pyrethroid formulations in PVC containers.